Wireless local area networks (WLAN) have developed to provide communication capabilities to various types of mobile devices. Such communication capabilities enable mobile devices to communicate with other devices in the network and beyond.
A typical WLAN has an interface point or access point (AP) to enable communications to, from, and/or between wireless devices within its network. An AP is the point of entry for wireless devices or mobile units (MU) into a network infrastructure. Additionally, an AP may itself be communicatively coupled to other network(s) including a wired network. Thus, an AP may manage communications between itself and other devices within its wireless network, communications between devices within its wireless network, and act as a bridge or gateway for communications between devices within its network and devices outside of its networks (e.g., devices on a wired network).
One type of WLAN has been specified in the Institute of Electrical and Electronics Engineers (IEEE) Standard 802.11-1997 and subsequent revisions. In an IEEE 802.11 compliant wireless network, various services are provided to establish and manage communications between an AP and MUs. Generally, an MU is registered, pre-subscribed, or otherwise authorized to access and/or communicate over the WLAN through the AP. For example, a WLAN may be deployed within a corporation. The corporation wishes to protect its computers and data that can be accessed over the network. Thus, an AP may limit access to the network to only pre-authorized MUs. A first mobile unit, being a pre-authorized device, would be allowed to communicate over the network. Meanwhile, a second mobile unit would be denied access to the network since it is not a pre-authorized device.
A typical network access protocol for an IEEE 802.11 compliant WLAN is herein described. Upon start-up or initialization, an MU with an IEEE 802.11 compliant interface attempts to find an existing WLAN infrastructure. The MU may listen to the information broadcasted by a WLAN station or AP. This information would allow the MU to locate AP, and then possibly to join its network. The MU may also start by sending out a message to solicit such information from a WLAN station or AP. The MU may then listen for a response from AP. The AP receiving such a request responds by sending a message with information that will allow the MU to locate the WLAN infrastructure. Once the MU has found an infrastructure, it may choose to join the WLAN by synchronizing its parameters.
If the MU decides to join a WLAN, it then proceeds by authentication/association handshakes. The authentication process is a mechanism for the MU to prove its identity. The IEEE 802.11 1997 WLAN specification supports two authentication services, Open System and Shared Key. These services function as low-level interfaces to negotiate access to the WLAN. Recent extensions of the IEEE 802.11 supports more enhanced authentication methods to improve security. Open System authentication is a default, null authentication procedure or algorithm. This procedure involves identity assertion, request for authentication, and an authentication result. Typically, an MU is already a network member, provides a password, and/or is pre-registered, in order to obtain access to the WLAN and its services via the authentication interface. Other authentication algorithms typically require MUs to know a secret key. The secret key may be delivered to an MU over a secure channel that may be protocol independent of the IEEE 802.11 standard (e.g., the IEEE 802.1× standard for instance).
Association is the mechanism through which an IEEE 802.11 compliant WLAN provides transparent mobility to stations or APs. Once a station successfully completes authentication/association handshakes with an AP, it may begin exchanging data frames with the AP and accessing network services.